In the field of electronic component mounting that electronic components are picked up from an electronic component feed unit by a nozzle, that is a component holding member, and mounted onto a board or other mounting object, it is practiced to measure the height size of the electronic component picked up by the nozzle for accurate mounting of the electronic component onto the board or other mounting object. The measured height size of the electronic component is fed back to nozzle height positioning control involved in mounting operation, and further collated with size data of the electronic component for judgment of a suck-up posture of the electronic component, by which any abnormal suckup which means that the electronic component is sucked up in a posture other than that with its mounting surface facing downward or the like is detected. As a result, mounting failures that the electronic component is mounted in an unstable state on the board or the like is prevented.
As the means for measuring the height size of an electronic component, one using a photoelectric sensor is known (see, e.g., Document 1: Japanese unexamined patent publication No. H11-298196 A). In this case, the height of an electronic component is measured through the steps of moving down the nozzle so that a laser beam projected from a separately placed beam projector to a beam receiver is orthogonally intersected by the nozzle, detecting nozzle height positions resulting at time points when the nozzle body and the electronic component picked up by the nozzle pass through the optical axis, respectively, and calculating the height of the electronic component from a difference between the nozzle height positions.